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Its because by some fluky chance, the moon rotates at the
same rate as the earth does so the near side is always
facing the earth, so even when its in shadow, its still
the same side. We can see more than half the sphere as
we can see it from different parts of the earth.

--
Vin
Melbourne, Australia
Remove no and spam from both sides of the @ sign email address to reply

Over the course of a lunar day (29.5 earth days) all sides of the moon
receive sunlight. If you are operating under the assumption that one
particular side of the moon *never* recieves light, you are mistaken.

The "dark side" of the moon refers to the "forbidden" side that is
never viewed directly from earth (or at least has not been viewed
directly for eons) because the same side of the moon always faces us.

Ahh..so what kind of light fill ratio should one use to bring out the
shadows nicely?

How much depth of field would you need to get the whole moon in focus?

Would you tell the moon to say "cheese"?

On 7-Apr-2004, John Popelish <> wrote:
> wrote:
> >
> > title says it all
>
> The Moon is lit by the Sun. The Sun is off to one side of the Moon.
> One side lit, one side dark. You would need two suns to light both
> sides at the same time.
>
> --
> John Popelish

> one side of the moon is heavier then the other. the heavy side was/is
> attracted by earth's gravity and over the many many years has stabilized so
> only one 'side' of the moon faces the earth.

This is completely off-topic, but it is not true. The point is tidal
forces. Tidal forces creates intense deformations in the moon when it
rotated, time ago. This deformations uses energy, obtained from its
rotation. So it slowly stopped. It could have been stopped in any other
position.

"Robert J. Kolker" wrote:
>
> wrote:
>
> > title says it all
>
> Any light seen from the Moon is relected light. Since the only
> significan t source of the light is from the Sun and there is only one
> Sun, then only one side of the Moon is lit up by the Sun.
>
> Bob Kolker
>

We (posters) should add that only half of the spheroid is illuminated,
a opposed to more than half, because the illumination source is far
enough away to approximate a point source.

wrote in message news:<40735763.7140.A8CBF0@localhost>...
> title says it all

Good question and I see you did not get a straight answer from the
physics "gurus" hanging out in this NG.

What is called a "dark side" of the moon is actually the "far side"
which is never seen by an observer on earth. But the moon gets sun
shine on all of its sides as it turns. The reason there is a "far
side" is that over the millions of years the moon goes around the
earth, the gravitational pull of the earth has slowed moon's rotation
about its axis down so it matches the period of its revolution around
the earth. One can easily see that when this is true there is always a
"far side" not seen by the earth and called the "dark side" but it
actually gets sun shine all over the place.

"Mike" <> wrote in message
news:...
> wrote in message
news:<40735763.7140.A8CBF0@localhost>...
> > title says it all
>
> Good question and I see you did not get a straight answer from the
> physics "gurus" hanging out in this NG.

In article <c50tbq$>, Nacho <> wrote:
>
>> one side of the moon is heavier then the other. the heavy side was/is
>> attracted by earth's gravity and over the many many years has stabilized so
>> only one 'side' of the moon faces the earth.
>
>This is completely off-topic, but it is not true.

Actually, he's quite right - although tidal forces are involved, your
explanation is trivially wrong:
>The point is tidal
>forces. Tidal forces creates intense deformations in the moon when it
>rotated, time ago. This deformations uses energy, obtained from its
>rotation. So it slowly stopped.

The problem with this is that the Moon hasn't actually stopped rotating at
all. It rotates on its axis once every 28 days. This is the same as its
orbital period, so that we always see the same side. If it had stopped, we'd
see opposite sides at 14 day intervals.

The reason the same side faces us is because the orbital and rotational
periods coincide. The reason they coincide is indeed because tidal forces
slow the rotation down, but, and this is the important bit, the Moon's
centre of mass is offset from its centre of rotation, like a bicycle wheel
that has a weight on one side. Over the N billion years that the Moon has
been orbiting the Earth, tidal forces have slowed the rotation until it
reached the optimal rotational speed, which is the speed where the Moon's
centre of gravity is always as close as possible to the centre of the Earth,
i.e. always facing down.

Guest

In article <4073da81$0$25661$>, (Obake) writes:
> In article <40735763.7140.A8CBF0@localhost>, wrote:
>>title says it all
>>
>
> one side of the moon is heavier then the other. the heavy side was/is
> attracted by earth's gravity and over the many many years has stabilized so
> only one 'side' of the moon faces the earth.

Under the tidal forces associated with the Earth's gravity, the
moon naturally assumes a slightly elongated shape -- something
like an egg. Those same tidal forces naturally pull the long axis
into alignment with the earth.

When the moon was rotating at a different speed than it revolved around
the Earth, it was something like a gushy soft-boiled egg -- always a
little elongated, but with various pieces of the lunar crust continuously
rotating into and out of the bulges. Since the moon is (or was) neither
completely rigid nor completely fluid, the viscosity would cause the
bulges to lag a little. And this would, in turn, cause a tidal torque,
eventually bringing the moon's rotation rate into lockstep with its
orbital period about the earth.

A moon that was merely heavy on one side would continue to spin
out of synch forever (*), much like an unbalanced frictionless
bicycle wheel. It takes a gushy satellite to efficiently lock up with
its partner.

I've never learned this out of a textbook in so many words, but it
seems pretty obvious.

John Briggs

(*) the rotation of an unbalanced satellite can eventually damp due to
other effects, but the time frames are much longer than the induced
tidal drag scenario described above.

"Mike" <> wrote in message
news:...
|
| Good question and I see you did not get a straight answer
| from the physics "gurus" hanging out in this NG.

Well, be fair. It wasn't clear whether itnwas a phase angle question or a
tidal locking question. Contrary to the original poster's statement, the
title did not say it all. I think both interpretations of the question were
answered courteously.

--
|
The universe is not required to conform | Jay Windley
to the expectations of the ignorant. | webmaster @ clavius.org

In sci.physics Sam Wormley <> wrote:
> "Robert J. Kolker" wrote:
>>
>> wrote:
>>
>> > title says it all
>>
>> Any light seen from the Moon is relected light. Since the only
>> significan t source of the light is from the Sun and there is only one
>> Sun, then only one side of the Moon is lit up by the Sun.
> We (posters) should add that only half of the spheroid is illuminated,
> a opposed to more than half, because the illumination source is far
> enough away to approximate a point source.

No, it's not.
Somewhere around an extra half a degree, or some extra 10Km of illumingation
round the edge of the illuminated area.

Anyway, the correct answer is that there has been a dark side of the
moon since 1973, as that's when the album was released.

"ZZBunker" <> wrote in message
news:...
> wrote in message
news:<40735763.7140.A8CBF0@localhost>...
> > title says it all
>
> Because the moon does not orbit the Earth,
> it is locked in Earth orbit.
>
> And also because the dark side of the moon
> is do much dark as it is colder than
> Mars.

Squishua wrote:
> On Wed, 07 Apr 2004 01:20:35 -0400, wrote:
> The "dark side" of the moon refers to the "forbidden" side that is
> never viewed directly from earth (or at least has not been viewed
> directly for eons) because the same side of the moon always faces us.

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